Recurring Deposit interest rate formula?

I want to find the rate of interest of a recurring deposit. suppose monthly inst. is Rs. 100, period is 24 months and maturity amount is Rs 2609. I want to find the Rate of interest. I want to know the formula for this. (Remember interest is quarterly compounded)

The following website will provide you the exact answer you are looking for, just insert the values that you know. I started by entering an assumed interest rate of 2.5 % and finally ended with an actual value of 3.95% by incrementing it by 0.1 or 0.05 etc. Assuning that you started with 100 and deposited 100 thereafter every month for two years and your final value was 2609.

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